1. Field of the Invention
The present invention relates to a ferrite sintered magnet.
2. Description of the Related Art
Hexagonal crystal based M-type (magnetoplumbite-type) Sr ferrite or Ba ferrite is known as a material of a permanent magnet consisting of an oxide. Magnetic materials consisting of these ferrites serve as a permanent magnet in the form of a ferrite sintered magnet, a bond magnet or the like.
In recent years, with the miniaturization and increasingly high performance of electronic components, permanent magnets have also been required to include high magnetic characteristics.
Residual magnetic flux density (Br) and coercivity (HcJ) are generally employed as indicators of magnetic characteristics of a permanent magnet. A permanent magnet is judged to have higher magnetic characteristics when these indicators are higher.
For example, Patent Document 1 shows a ferrite magnetic material having high Br and HcJ but also high Hk/HcJ by containing a certain amount of a Si component.
Patent Document 2 shows a ferrite magnetic material having high Br and HcJ by containing a certain amount of a Si component and further containing a certain amount of an Al component and a Cr component.
As mentioned above, combinations of elements added to main components have been variously changed in order to obtain both good Br and HcJ, but it is still unclear what kind of combination of added elements provides high magnetic characteristics.
In addition to having higher Br and HcJ, it is preferable for a permanent magnet to also have a high ratio of a value (Bk) of a magnetic field when magnetization is 90% of Br to HcJ, which is a so-called squareness ratio (Hk/HcJ).
However, it has never been easy to obtain a permanent magnet having such three magnetic characteristics, since when one of these three magnetic characteristics improves, the other magnetic characteristics end up lowering, for example.
Patent Document 1: WO 2011/004791
Patent Document 2: WO 2014/021426